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Journal Articles

Evaluation of local damage to reinforced concrete panels subjected to oblique impact by soft missile

Nishida, Akemi; Kang, Z.; Nagai, Minoru*; Tsubota, Haruji; Li, Y.

Nuclear Engineering and Design, 350, p.116 - 127, 2019/08

Many empirical formulas have been proposed for evaluating local damage to reinforced concrete structures caused by impacts of rigid missiles. Most of these formulas have been derived based on tests involving impact normal to target structures. Thus far, few tests with oblique impact onto target structures have been carried out. As a final goal of this research, we aim to propose a new formula for evaluating the local damage caused by oblique impact based on previous experimental and simulation results. In this study, we perform simulation analyses for evaluating the local damage to reinforced concrete panels subjected to oblique impacts with various angle by soft missiles under various impact velocities using a simulation method that was validated using the results of previous impact experiments. In this paper, the investigated results and obtained knowledges from them are shown.

Journal Articles

Impact assessment on local damage to reinforced concrete panels by different projectiles; Impact behavior for projectiles with hemispherical nose shape

Kang, Z.; Nagai, Minoru*; Nishida, Akemi; Tsubota, Haruji; Li, Y.

Proceedings of 25th International Conference on Structural Mechanics in Reactor Technology (SMiRT-25) (USB Flash Drive), 10 Pages, 2019/08

Many empirical formulae have been proposed for evaluating the local damage to reinforced concrete (RC) structures caused by rigid projectile impact. The majority of these formulae aim at impact tests perpendicular to target structures, while few impact tests oblique to the target structure have been studied. The final objective of this study is to propose a new formula for evaluating the local damage to RC structures caused by oblique impact based on past experimental and simulation results. Up to now, we validated the analytical method by comparison with the experimental results and conduct the simulation analysis of impact assessment on RC panel by rigid/soft projectile with flat nose shape using the validated approach. In the part 1 of this paper, the same analytical method is used to simulate the local damage to RC panels caused by oblique impact of rigid/soft projectile with hemispherical nose shape. The results associated with penetration depth of RC structure, energy contribution ratio, etc. are presented.

Journal Articles

Plastic collapse stresses based on flaw combination rules for pipes containing two circumferential similar flaws

Hasegawa, Kunio; Li, Y.; Kim, Y.-J.*; Lacroix, V.*; Strnadel, B.*

Journal of Pressure Vessel Technology, 141(3), p.031201_1 - 031201_5, 2019/06

When discrete multiple flaws are in the same plane, and they are close to each other, it can be determined whether they are combined or standalone in accordance with combination rules provided by Fitness-For-Service (FFS) codes. However, specific criteria of the rules are different amongst these FFS codes. On the other hand, plastic collapse bending stresses for stainless steel pipes with two circumferential similar flaws were obtained by experiments and the prediction procedure for collapse stresses for pipes with two similar flaws were developed analytically. Using the experimental data and the analytical procedure, plastic collapse stresses for pipes with two similar flaws are compared with the stresses in compliance with the flaw combination criteria. It is shown that the calculated plastic collapse stresses based on the flaw combination criteria are significantly different from the experimental and analytical stresses.

Journal Articles

Evidence for singular-phonon-induced nematic superconductivity in a topological superconductor candidate Sr$$_{0.1}$$Bi$$_{2}$$Se$$_{3}$$

Wang, J.*; Ran, K.*; Li, S.*; Ma, Z.*; Bao, S.*; Cai, Z.*; Zhang, Y.*; Nakajima, Kenji; Kawamura, Seiko; $v{C}$erm$'a$k, P.*; et al.

Nature Communications (Internet), 10, p.2802_1 - 2802_6, 2019/06

Journal Articles

Influence evaluation of sampling methods of the non-destructive examination on failure probability of piping based on probabilistic fracture mechanics analyses

Mano, Akihiro; Katsuyama, Jinya; Li, Y.

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 7 Pages, 2019/05

In Japanese nuclear power plants, non-destructive examinations (NDEs) are performed for welds in piping in accordance with the rules such as Rules on Fitness-for-Service for Nuclear Power Plant of the Japan Society of Mechanical Engineers (JSME FFS). A set of NDEs is performed in each 10-year interval, and the extent of examination in each interval is specified in the rules. Welding lines to be examined are selected considering the extent of examination based on two sampling methods. One is the fixed location sampling method that welds to be examined are selected from welds examined in the last interval. The other is the random location sampling method that welds to be examined are selected from other than welds examined in the last interval. The selection of the sampling methods is considered to be one of the important factors in in-service inspection. Probabilistic fracture mechanics (PFM) analysis is expected to be more rational method for the structural integrity assessment because it can consider the uncertainties of various influence factors and evaluate the quantitative values such as failure probability of a cracked component as the solution. In this study, we investigated the influence of the sampling methods related to the NDE on failure probability of typical nuclear piping based on PFM analyses. Through sensitivity PFM analyses, we confirmed that failure probability value obtained from PFM analysis is useful as a quantitative numerical index for selecting the sampling method in an in-service inspection.

Journal Articles

Simulation analysis on local damage to reinforced concrete panels subjected to oblique impact by different projectiles, 1; Comparison of impact behavior for rigid projectiles with flat and hemispherical nose shape

Kang, Z.; Nagai, Minoru*; Nishida, Akemi; Tsubota, Haruji; Li, Y.

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 9 Pages, 2019/05

Many empirical formulae have been proposed for evaluating the local damage to reinforced concrete (RC) structures caused by rigid projectile impact. The majority of these formulae aim at impact tests perpendicular to target structures, while few impact tests oblique to the target structure have been studied. The final objective of this study is to propose a new formula for evaluating the local damage to RC structures caused by oblique impact based on past experimental and simulation results. The finite element code LS-DYNA R7.1.2 is used to perform the numerical analysis by adopting Lagrangian finite elements and explicit time integration. So far, we validated the analytical method by comparison with the experimental results and conduct the simulation analysis of impact assessment on RC panel by rigid/soft projectile with flat nose shape using the validated approach. Results of reduction coefficient with respect to rigid/soft projectile and impact angle were obtained. Therefore, in this study, we focus on the impact problems caused by rigid projectile with hemispherical nose shape. The same analytical method is used to simulate the local damage to RC panels caused by oblique impact of rigid projectile with hemispherical nose shape. The results associated with penetration depth of RC structure, energy contribution ratio, etc. are presented. According to the comparison analysis of results of local damage to RC structure by rigid projectiles with flat and hemispherical nose shape, the influence of different nose shapes of rigid projectile on the local damage of RC panels caused by oblique impact is investigated.

Journal Articles

Verification of a probabilistic fracture mechanics code PASCAL4 for reactor pressure vessels

Lu, K.; Katsuyama, Jinya; Li, Y.; Miyamoto, Yuhei*; Hirota, Takatoshi*; Itabashi, Yu*; Nagai, Masaki*; Suzuki, Masahide*; Kanto, Yasuhiro*

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 9 Pages, 2019/05

Journal Articles

Simulation analysis on local damage to reinforced concrete panels subjected to oblique impact by different projectiles, 2; Comparison of impact behavior for soft projectiles with flat and hemispherical nose shape

Nagai, Minoru*; Kang, Z.; Nishida, Akemi; Tsubota, Haruji; Li, Y.

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05

In this study, the final purpose is to propose a new formula for evaluating the local damage caused by oblique impact based on past experimental results and previous research achievements. Up to now, we validated the analytical method by comparison with the experimental results and conducted simulation analysis associated with impact assessment on RC panel by soft/rigid projectile with flat nose shape using the validated approach. In the part 1 of this study, the same procedure of our previous work is followed to investigate the local damage to RC panel caused by rigid projectile with flat and hemispherical nose shape. In the part 2, we focus on the comparison analysis of simulation results of local damage to RC panel subjected to oblique impact by soft missile with flat and hemispherical nose shape. The structural damage of RC panel and projectiles, energy contribution ratio, etc. is studied for each case. The results indicate the difference of nose shape of projectile is of great importance to influence the penetration depth generated by oblique impact of soft projectile.

Journal Articles

Expansion of high temperature creep test data for failure evaluation of BWR lower head in a severe accident

Yamaguchi, Yoshihito; Katsuyama, Jinya; Kaji, Yoshiyuki; Osaka, Masahiko; Li, Y.

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 7 Pages, 2019/05

After the Fukushima Daiichi (1F) Nuclear Power Plant accident, we have been developing a prediction method for rupture time and location considering creep damage mechanisms using finite element analysis for early completion of the decommissioning of nuclear power plants in 1F. We have also been obtaining material properties at high temperature near the melting point which are not provided in existing database or literature for the finite element analysis. In this study, we performed uni-axial tensile and creep tests for low alloy steel, Ni-based alloy steel and stainless steels and expanded existing database of material properties. Especially, creep data with longer rupture time at high temperature were obtained by a creep test equipment with a noncontact measurement system. To improve the accuracy of failure evaluation under severe accident conditions, we determined parameters of creep constitutive law based on the expanded database.

Journal Articles

Plastic collapse stresses for pipes with inner and outer circumferential cracks

Mares, V.*; Hasegawa, Kunio; Li, Y.; Lacroix, V.*

Journal of Pressure Vessel Technology, 141(2), p.021203_1 - 021203_6, 2019/04

 Percentile:100(Engineering, Mechanical)

Appendix C-5320 of ASME BPV Code Section XI provides an equation of bending stress at the plastic collapse, where the equation is applicable for both inner and outer surface cracks. That is, the collapse stresses for pipes with inner and outer surface cracks are the same. Authors considered the separated pipe mean radii at the cracked ligament and at the un-cracked ligament and equations of plastic collapse stresses for both inner and outer cracked pipes were developed. As the results of the calculations, when the crack angle and depth are the same, the collapse stress for outer cracked pipe is lower than that calculated by the Appendix C equation. It is found that the Appendix C equation gives un-conservative plastic collapse stress.

Journal Articles

Negative Te spin polarization responsible for ferromagnetic order in the doped topological insulator V$$_{0.04}$$(Sb$$_{1-x}$$Bi$$_{x}$$)$$_{1.96}$$Te$$_{3}$$

Ye, M.*; Xu, T.*; Li, G.*; Qiao, S.*; Takeda, Yukiharu; Saito, Yuji; Zhu, S.-Y.*; Nurmamat, M.*; Sumida, Kazuki*; Ishida, Yukiaki*; et al.

Physical Review B, 99(14), p.144413_1 - 144413_7, 2019/04

 Percentile:100(Materials Science, Multidisciplinary)

Journal Articles

Failure bending moment of pipes containing multiple circumferential flaws with complex shape

Li, Y.; Azuma, Kisaburo*; Hasegawa, Kunio

International Journal of Pressure Vessels and Piping, 171, p.305 - 310, 2019/03

Journal Articles

Colossal barocaloric effects in plastic crystals

Li, B.*; Kawakita, Yukinobu; Kawamura, Seiko; Sugahara, Takeshi*; Wang, H.*; Wang, J.*; Chen, Y.*; Kawaguchi, Saori*; Kawaguchi, Shogo*; Ohara, Koji*; et al.

Nature, 567(7749), p.506 - 510, 2019/03

Refrigeration is of vital importance for modern society for example, for food storage and air conditioning- and 25 to 30% of the world's electricity is consumed for refrigeration. Current refrigeration technology mostly involves the conventional vapour compression cycle, but the materials used in this technology are of growing environmental concern because of their large global warming potential. As a promising alternative, refrigeration technologies based on solid-state caloric effects have been attracting attention in recent decades. However, their application is restricted by the limited performance of current caloric materials, owing to small isothermal entropy changes and large driving magnetic fields. Here we report colossal barocaloric effects (CBCEs) (barocaloric effects are cooling effects of pressure-induced phase transitions) in a class of disordered solids called plastic crystals. The obtained entropy changes in a representative plastic crystal, neopentylglycol, are about 389 joules per kilogram per kelvin near room temperature. Pressure-dependent neutron scattering measurements reveal that CBCEs in plastic crystals can be attributed to the combination of extensive molecular orientational disorder, giant compressibility and highly anharmonic lattice dynamics of these materials. Our study establishes the microscopic mechanism of CBCEs in plastic crystals and paves the way to next-generation solid-state refrigeration technologies.

Journal Articles

Pressure-induced Diels-Alder reactions in C$$_{6}$$H$$_{6}$$ - C$$_{6}$$F$$_{6}$$ cocrystal towards graphane structure

Wang, Y.*; Dong, X.*; Tang, X.*; Zheng, H.*; Li, K.*; Lin, X.*; Fang, L.*; Sun, G.*; Chen, X.*; Xie, L.*; et al.

Angewandte Chemie; International Edition, 58(5), p.1468 - 1473, 2019/01

Pressure-induced polymerization (PIP) of aromatics is a novel method to construct sp$$^{3}$$-carbon frameworks, and nanothreads with diamond-like structures were synthesized by compressing benzene and its derivatives. Here by compressing benzene-hexafluorobenzene cocrystal(CHCF), we identified H-F-substituted graphane with a layered structure in the PIP product. Based on the crystal structure determined from the in situ neutron diffraction and the intermediate products identified by the gas chromatography-mass spectrum, we found that at 20 GPa CHCF forms tilted columns with benzene and hexafluorobenzene stacked alternatively, which leads to a [4+2] polymer, and then transfers to short-range ordered hydrogenated-fluorinated graphane. The reaction process contains [4+2] Diels-Alder, retro-Diels-Alder, and 1-1' coupling, and the former is the key reaction in the PIP. Our studies confirmed the elemental reactions of the CHCF for the first time, which provides a novel insight into the PIP of aromatics.

Journal Articles

Nuclear structure of $$^{76}$$Ni from the ($$p$$,$$2p$$) reaction

Elekes, Z.*; Kripk$'o$, $'A$*; Sohler, D.*; Sieja, K.*; Ogata, Kazuyuki*; Yoshida, Kazuki; Doornenbal, P.*; Obertelli, A.*; Authelet, G.*; Baba, Hidetada*; et al.

Physical Review C, 99(1), p.014312_1 - 014312_7, 2019/01

 Percentile:100(Physics, Nuclear)

The nuclear structure of the $$^{76}$$Ni nucleus was investigated by ($$p$$,$$2p$$) reaction using a NaI(Tl) array to detect the deexciting prompt $$gamma$$ rays. A new transition with an energy of 2227 keV was identified by $$gamma gamma$$ and $$gamma gamma gamma$$ coincidences. Our shell-model calculations using the Lenzi, Nowacki, Poves, and Sieja interaction produced good candidates for the experimental proton hole states in the observed energy region, and the theoretical cross sections showed good agreement with the experimental values. Although we could not assign all the experimental states to the theoretical ones unambiguously, the results are consistent with a reasonably large Z = 28 shell gap for nickel isotopes in accordance with previous studies.

Journal Articles

Influence evaluation of loading conditions during pressurized thermal shock transients based on thermal-hydraulics and structural analyses

Katsuyama, Jinya; Uno, Shumpei*; Watanabe, Tadashi*; Li, Y.

Frontiers of Mechanical Engineering, 13(4), p.563 - 570, 2018/12

For the structural integrity assessments on reactor pressure vessels (RPVs) under pressurized thermal shock (PTS) events, thermal hydraulic (TH) behavior of coolant water is one of the most important influence factors. Configuration of plant equipment and their dimensions, and operator action have large influences on TH behavior. In this study, to investigate the influence of operator action on TH behavior during a PTS event, we developed an analysis model for a typical Japanese plant, and performed TH and structural analyses. Two different operator action times were assumed based on the Japanese and US' rules. From the analysis results, it was clarified that differences in operator action times have a significant effect on TH behavior and loading conditions, that is, following the Japanese rule may lead to lower stresses compared to that when following the US rule because earlier operator action caused lower pressure in the RPV.

Journal Articles

Evidence of a structure in $$bar{K}^{0} Lambda _{c}^{+}$$ consistent with a charged $$Xi _c(2930)^{+}$$, and updated measurement of $$bar{B}^{0} rightarrow bar{K}^{0} Lambda _{c}^{+} bar{Lambda }_{c}^{-}$$ at Belle

Li, Y. B.*; Tanida, Kiyoshi; Belle Collaboration*; 175 of others*

European Physical Journal C, 78(11), p.928_1 - 928_8, 2018/11

Journal Articles

Failure behavior analyses of piping system under dynamic seismic loading

Udagawa, Makoto; Li, Y.; Nishida, Akemi; Nakamura, Izumi*

International Journal of Pressure Vessels and Piping, 167, p.2 - 10, 2018/11

 Percentile:100(Engineering, Multidisciplinary)

It is important to assure the structural Integrity of piping systems under severe earthquakes because those systems comprise the pressure boundary for coolant with high pressure and temperature. In this study, we examine the seismic safety capacity of piping systems under severe dynamic seismic loading using a series of dynamic-elastic-plastic analyses focusing on dynamic excitation experiments of 3D piping systems which was tested by NIED. Analytical results were consistent with experimental data in terms of natural frequency, natural vibration mode, response accelerations, elbow opening-closing displacements, strain histories, failure position, and low-cycle fatigue failure lives. Based on these results, we concluded that the analytical model used in the study can be applied to failure behavior evaluation for piping systems under severe dynamic seismic loading.

Journal Articles

Stress intensity factors for transformed surface flaws and remaining fatigue lives based on flaw-to-surface proximity rules

Hasegawa, Kunio*; Strnadel, B.*; Li, Y.; Lacroix, V.*

Journal of Pressure Vessel Technology, 140(5), p.051204_1 - 051204_7, 2018/10

 Percentile:100(Engineering, Mechanical)

Journal Articles

A Fluorometric skin-interfaced microfluidic device and smartphone imaging module for ${{it in situ}}$ quantitative analysis of sweat chemistry

Sekine, Yurina; Kim, S. B.*; Zhang, Y.*; Bandodkar, A. J.*; Xu, S.*; Choi, J.*; Irie, Masahiro*; Ray, T. R.*; Kohli, P.*; Kozai, Naofumi; et al.

Lab on a Chip, 18(15), p.2178 - 2186, 2018/08

The rich composition of solutes and metabolites in sweat and its relative ease of collection upon excretion from skin pores make this class of biofluid an attractive candidate for point of care analysis. Here, we present a complementary approach that exploits fluorometric sensing modalities integrated into a soft, skin-interfaced microfluidic system which, when paired with a simple smartphone-based imaging module, allows for in-situ measurement of important biomarkers in sweat. A network array of microchannels and a collection of microreservoirs pre-filled with fluorescent probes that selectively react with target analytes in sweat (e.g. probes), enable quantitative, rapid analysis. Field studies on human subjects demonstrate the ability to measure the concentrations of chloride, sodium and zinc in sweat, with accuracy that matches that of conventional laboratory techniques.

276 (Records 1-20 displayed on this page)